This invention relates generally to air conditioning systems. More particularly the invention relates to an improved ceiling mounted indoor unit of an air conditioning system.
Ductless split air conditioning systems are usually found in residential and small commercial applications. Unlike a ducted split system, in which there is a central indoor unit with conditioned air being distributed to rooms by ducting, a ductless split system has one or more indoor units located in the room(s) served by the system. The term "split" refers to the configuration of the entire system as being split into indoor and outdoor units. Both a ducted and a ductless split system provide one heat exchanger in an outdoor unit located external to the space to be conditioned, while another heat exchanger is located in an indoor unit. In a ductless split system refrigerant lines running between the indoor and outdoor units interconnect the two heat exchangers and the compressor. There are usually fans associated with both the indoor and outdoor heat exchangers.
It is common to mount the indoor unit of a ductless split air conditioner at a high position in the room it is to serve. The indoor unit may be mounted on a wall or hung from the ceiling. If the room has a false ceiling, the indoor unit may be recessed into the false ceiling so as to make it as unobtrusive as possible. False ceilings are usually constructed of a relatively porous material which is sound absorbent.
An important objective in the design of an air conditioning system is low radiated noise levels. The primary source of noise in an indoor unit is the fan, with the noise being radiated primarily from the air discharge opening but also from the air inlet opening.
Another important design objective is that there be good air flow distribution within the room to be conditioned. Because warm air rises, it may collect and become stratified at or near the ceiling level in a room. This is undesirable in either the heating or cooling modes of operation. A recessed ceiling mounted indoor unit will not normally recirculate this stratified air unless it has inlet louvers that project outwardly and downwardly from the main portion of the unit, and such louvers tend to detract from the appearance of the unit.
In a typical indoor unit, the air suction inlet and air discharge outlet are located relatively close to each other. In such a unit, there can be a significant proportion of the total air flow through the unit that "short circuits" from discharge to suction thus reducing the amount of air recirculated through the entire volume of the room served.